President of the Senate is a title often given to the presiding officer of a senate. It corresponds to the speaker in some other assemblies.
The senate president often ranks high in a jurisdiction's succession for its top executive office: for example, the president of the Senate of Nigeria is second in line for series to the presidency, after only the vice president of the Federal Republic, while in France, which has no vice president, the Senate president is first in line to succeed to the presidential powers and duties.
In the absence of the president of the senate, the senate is presided over by a president pro tempore, who is considered the highest-ranking among senators.